1. Technical Field
This invention relates generally to antenna systems and, more particularly, to a multifunction antenna system and method for providing controllable and adaptive antenna beam patterns with a multiple arm spiral antenna.
2. Discussion
Modern avionics systems and the like generally require multifunction antennas in order to meet operating requirements which are typically imposed. Such requirements include the transmission and reception of long range signals with optimal beam patterns over a wide field of view. Another requirement is the ability to provide a plurality of operating modes with a single antenna aperture that may be used to support multiple avionics functions. In addition, wide frequency bandwidth requirements have generally been imposed which allow for a larger number of multifunction operations. Requirements such as these have generally been imposed on electronic warfare (EW) and communications, navigation and identification (CNI) waveforms and operating modes for modern antenna systems.
To increase the communication link range of long range operating modes, a high gain antenna pattern is generally required in order to provide increased gain in a particular direction. Similarly, if an undesirable interfering source is detected in a particular direction, generally an antenna null should be produced in that direction in order to reduce the strength of the jamming signal received. Conventional antenna systems have been developed which provide for a predetermined beam pattern, however, such antenna systems generally have not provided for multifunction and adaptive beamforming capabilities.
In particular, multiple arm spiral antennas (MASA) have been developed for providing enhanced wide field of view antenna operations. The conventional MASA generally includes multiple cylindrically symmetric spiral arm elements which transmit and receive radiating signals in a predetermined beam pattern. The conventional MASA is generally limited to the single predetermined beam pattern and is therefore limited to applications which operate with a single beam pattern. As a result, the conventional MASA generally does not allow for multifunction operations. In addition, the conventional MASA generally does not provide for enhanced multiple operating modes with controllable beam patterns or adaptive beam forming capabilities.
It is therefore desirable to provide for an enhanced multifunction antenna system for transmitting and receiving signals in a controllable beam pattern. It is further desirable to provide for such an antenna system which may select amongst a plurality of beam patterns to provide multiple operating functions. In particular, it is desirable to provide for an antenna system which may transmit and receive a steered beam with increased gain in a particular direction and/or produce a steered null in a desired direction. In addition, it is also desirable to provide for such an antenna system which produces a beam pattern with multiple simultaneous beams and nulls. Furthermore, it is further desirable to provide for such an antenna system which has adaptive beamforming capabilities.